As far as the service offered, textbroker is hands down the best option. That's not to say it's not without bugs. Basically publishers list articles they'd like written, then writers claim the articles they'd like to write.
This means that articles may go unwritten. Additionally you've got to hand approve each and every article you order, and some authors do seem to write right into the text box on the Textbroker page, therefor failing to use the spelling and grammar checking tools provided by Microsoft Word.
Overall though, Textbroker.com is a great option for article-writing on the cheap.
It's also a great place to get started working at home as a writer. You will NOT make millions, but you'll get experience, and begin making a name for yourself, building that portfolio, etc.